Print hammer with moving coil

ABSTRACT

A printer is provided with a plurality of pivoted print hammers having flat operating windings which are positioned in a plurality of parallel air gaps between projecting pole pieces of an electromagnet.

United States Patent 1191 Meier 1 Dec. 25, 1973 [5 PRINT HAMMER WITH MOVING COIL 3,543,906 12/1970 Hladky 101/93 c x 3,643,595 2/1972 Helms et a1. 101/93 C [75] Inventor: khan 3,282,203 11/1966 KaibaCh et a1. 1 101 93 c [73] Assignee: International Business Machines 3 23332; 2233? a g ar Corpnmmn Armonk 3.605.611 9/1971 Konkel 6:61 101/93 C [22] Filed: Dec. 20, 1971 Prima Examiner-Robert E. Pulfrey 21 A 11v 209512 1 pp 0 Assistant Examiner-E. M. Coven Attorney-Francis V. Giolma et a1. [52] US. Cl. 101/93 C, 335/281 [51] Int. Cl B4lj 7/08 [58] Field of Search 101/93 C; 335/281 [57] AB STRACT A printer is provided w1th a plurality of pivoted print [56] References Cited hammers having flat operating windings which are po- UNITED STATES PATENTS sitioned in a plurality of parallel air gaps between pro- 3 I72 352 H H I t 3 C jecting pole pieces of an electromagnet.

e ms e a 3,564,999 2/1971 De Puy et al. 101/93 C 5 Claims, 7 Drawing Figures PRINT HAMMER WITH MOVING COIL FIELD OF THE INVENTION The invention relates generally to printers and it has reference in particular to printers having print hammers activated by pulsing an operating winding which moves in an air gap between pole pieces of a magnet.

DESCRIPTION OF THE PRIOR ART Printers are known in the prior art wherein moving coil type print hammers have the coils moving in serially-related air gaps between pole pieces of permanent magnets such as disclosed in U. S. Pat. No. 3,285,166, which issued on Nov. 15, 1966, to C. .I. Helms et al.

SUMMARY OF THE INVENTION Generally stated, it is an object of this invention to provide an improved print hammer for a printer.

More specifically, it is an object of this invention to provide an improved print hammer structure wherein the operating coils of a plurality of print hammers move in parallel air gaps between a plurality of poles pieces of a magnet structure.

Another object of the invention is to provide a more efficient magnet structure for a plurality of moving coil print hammers wherein a plurality of pole pieces are arranged with parallel air gaps thus providing a magnetic structure having a lower magnetic reluctance.

It is also an object of the invention to provide a high performance, low cost print hammer.

Yet another object of the invention is to provide a moving coil print hammer structure in which the coils move in a plurality of parallel air gaps, which minimize magnetic reactions between adjacent print hammers.

It is also an object of this invention to provide in a pivoted type moving coil print hammer for using a trapezoidal-shaped coil with the opposite sides so inclined as to be radially disposed with respect to the armature pivot.

Yet another object of the invention is to provide for using compression-type springs to maintain a print hammer in a rest position against adjustable return stop screws and also conduct current to the operating coil mounted on the print hammer.

In a preferred form a plurality of print hammers are pivotally supported in side-by-side relation and are provided with relatively flat operating coils which are positioned between projecting pole pieces from magnet plates connected by a magnet core having a continuously energized magnet coil which provides a plurality of pairs of parallel air gaps in which the moving coil sides are positioned. The moving coils are electrically connected by means of compression-type restore springs to a source so as to be pulsed to cause the hammers to move and impact a document for printing.

The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of a preferred embodiment of the invention as illustrated in the accompanying drawing.

DESCRIPTION OF THE DRAWING In the drawing:

FIG. 1 is a schematic view in side elevation of a print hammer structure embodying the invention in one of its forms;

FIG. 2 is a cross-section view of the inclined leg portions 16a and 16b, which are connected at the ends, and are inclined FIG. 3 is a side elevation view of the magnet and coil structure of FIG. 1 showing one pair of corresponding pole pieces connected to the north and south pole plates, respectively;

FIG. 4 is a similar view to FIG. 3 showing the other one of an adjacent pair of corresponding pole pieces;

FIG. 5 is a section view taken along the line 55 of FIGS. 3 and 4', 7

FIG. 6 is a partly-sectioned partial plan view along the line 6-6 of FIG. I; and

FIG. 7 is a section view taken along the line 77 of FIGS. 3 and 4. 5

DESCRIPTION OF A PREFERRED EMBODIMENT Referring to FIG. 1, the reference numeral 10 denotes generally a print hammer structure in which a print hammer 12 having a hammer face 12a at one end is mounted on a pivot 14 adjacent the other end and is operated by means of an operating coil 16 mounted on the print hammer intermediate said ends by means of an intermediate support 18 for movement in air gaps between pole pieces of an electromagnet Structure 20. Compression-type springs 22 and 24 are positioned between a depending tail piece 26 of the intermediate support 18 and a spring and terminal block 28, which may be secured by means of a block support 30 for biasing the hammer 12 to a normal rest position against a stop screw 29. The springs 22 and 24 provide electrical connections to the coil 16 through conductors 23 and 25 secured in the support 18.

As shown in FIG. 2, the operating coil 16 has flanged side pieces 32, which project beyond the sides of the coil 16 and are spaced apart so as to receive a projecting web 34 of the intermediate support 18 to which it may be secured by cementing or the like. The intermediate support 18 itself has spaced apart flanges 36, which receive the body portion of the print hammer l2 and to which they are secured. Referring to FIGS. 1, 3 and 4, it will be seen that the electromagnet 20 comprises spaced apart pole plates 40 and 42 having a connecting core portion 46 therebetween about which is positioned an operating coil 48 which may be continuously energized to provide magnetic flux. The pole plates 40 and 42 may be either provided with a single connecting core member 46 or as shown in FIG. 7, may be provided with two spaced core members 46 and 47. The pole plates 40 and 42 may be provided with spaced apart alternately long and short projecting pole pieces 50 and 52 and 54 and 56, respectively. The adjacent Pole Pieces 50 and 52 of the pole plate 40 are spaced apart, as shown in FIG. 6, having a slot 60 therebetween. The pole pieces 50 and 52 are generally L- shaped and have depending tapered end portions 62 and 64, respectively, with the end portions 62 being further away from the connecting core member 46 than the depending end portions 64. The pole pieces 54 and 56 are similarly arranged with upturned tapered end portions 66 and 68, respectively, which are alternately closer to and further away from the connecting core member 46. The pole pieces 50 and 54 are in the same plane, and the pole pieces 52 and 56 are in a common plane adjacent to, but spaced from, the pole pieces 50 and 54 by intervening gaps 60. The coils 16 lie in the gaps 60 between the adjacent pairs of pole pieces 50,

52 and 54, 56, as shown in FIGS. 5 and 6. As shown in FIGS.'1, 3 and 4, the coils l6tare trapezoidal in shape and have inclined side portions 16a and 16b, which are inclined so as to lie. along radii which pass through the mounting pivot 14 of the print hammer 12. Since the magnetic flux from a pole plate 40 will pass from the other pole piece 50 to the adjacent overlapping pole piece 56 of the pole plate 42, in each instance, this provides a plurality of pairs of parallel-related air gaps in which the legs 16a .of the operating coils 16 are positioned. The plurality of inner pole pieces 54 and 52 likewise provide another plurality of parallel-related air gaps in which the legs 16b of the operating coils 16 will be positioned. This relationship is shown more clearly in FIG. 5, which is a cross-section view taken along the lines 5-5 of either FIG. 3 or FIG. 4. It will be seen that the air gap 60 between the upper pair of pole pieces 62 and 68 of FIG. 5 is in parallel relation with the air gap 60 between the lower pole piece 68 and the next adjacent pole piece 62. Likewise, the air gap 60 between the inner pole pieces 66 and 64 is in parallel relation with the air gap between the pole piece 64 and the next adjacent pole piece 66.

A thin coil 16 is imperative for all moving coil designs in order to obtain sufficient magnetic flux through the gap 60 with a reasonable number of ampereturns. For the proposed design, a 40 mils thick coil is contemplated consisting of two mils insulating flanges 32 and a 20 mils layer of wire. Calculations show it should r'eadily be possible to obtain 70,000

ergs of print energy from a moving coil hammer of the type disclosed when energizing the operating coil with 3 amperes at 42 volts. This type of hammer has a relatively high I performance and relatively low cost. Its

efficiency or energy conversion is relatively good.

While the invention has been shown and described with reference to a preferred embodiment thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.

What is claimed is:

I. In printing apparatus a plurality of movable print hammers,

a relatively flat operating coil secured to each of said print hammers, each such coil having relatively straight spaced apart leg portions connected together at each end,

means for providing a plurality of pairs of parallel air gaps to receive said leg portions of said coils including a magnetic structure having elongated coextensive spaced apart north and south pole plates of magnetic material each having a plurality of alternately long and short relatively thin pole pieces projecting laterally to one side of said pole plate with end portions of the pole pieces of each pole plate inturned toward the pole pieces of the other pole plate and said end portions being arranged in interleaved relation with a long pole piece of said northpole plate lying in the same plane but spaced from a short pole piece of said south poleplate, and a first air gap between said long pole piece of said north pole plate and an adjacent long pole piece of said south pole plate, and a second coplanar air gap between a corresponding short pole piece of said north pole plate and the adjacent short pole piece of said south pole plate, said coil being positioned with one of said spaced apart leg portions in each of said first and second coplanar air gaps,

means positioned between said north and south pole plates for producing a magnetic flux field in said pairs of parallel air gaps and means providing electrical connections to said coil for selectively energizing said coil to operate said print hammer.

2. The invention as defined in' claim 1 characterized by each of said print hammers having a hammer face at one end and being pivotally supported on pivot means adjacent the other end, and having said coil secured thereto intermediate its ends.

3. In the invention as defined in claim 2 characterized by said operating coils being trapezoidal in shape with said leg portion being inclined toward each other at one end and disposed in substantially radial relation with said pivot means.

4. The invention as defined in claim 1 characterized by said pole plates having connecting core portions and said means for producing magnetic flux between said north and south pole plates comprises a pair of windings positioned about said core portions connecting said pole plates.

5. The invention as defined in claim 2 characterized by said other end of said print hammer projecting beyond said pivot means, and further characterized by compression spring means engaging said projecting portion for biasing the print hammer to a rest position, said compression spring means being electrically connected to the operating coil for effecting selective energization thereof. 

1. In printing apparatus a plurality of movable print hammers, a relatively flat operating coil secured to each of said print hammers, each such coil having relatively straight spaced apart leg portions connected together at each end, means for providing a plurality of pairs of parallel air gaps to receive said leg portions of said coils including a magnetic structure having elongated coextensive spaced apart north and south pole plates of magnetic material each having a plurality of alternately long and short relatively thin pole pieces projecting laterally to one side of said pole plate with end portions of the pole pieces of each pole plate inturned toward the pole pieces of the other pole plate and said end portions being arranged in interleaved relation with a long pole piece of said north pole plate lying in the same plane but spaced from a short pole piece of said south pole plate, and a first air gap between said long pole piece of said north pole plate and an adjacent long pole piece of said south pole plate, and a second coplanar air gap between a corresponding short pole piece of said north pole plate and the adjacent short pole piece of said south pole plate, said coil being positioned with one of said spaced apart leg portions in each of said first and second coplanar air gaps, means positioned between said north and south pole plates for producing a magnetic flux field in said pairs of parallel air gaps and means providing electrical connections to said coil for selectively energizing said coil to operate said print hammer.
 2. The invention as defined in claim 1 characterized by each of said print hammers having a hammer face at one end and being pivotally supported on pivot means adjacent the other end, and having said coil secured thereto intermediate its ends.
 3. In the invention as defined in claim 2 characterized by said operating coils being trapezoidal in shape with said leg portion being inclined toward each other at one end and disposed in substantially radial relation with said pivot means.
 4. The invention as defined in claim 1 characterized by said pole plates having connecting core portions and said means for producing magnetic flux between said north and south pole plates comprises a pair of windings positioned about said core portions connecting said pole plates.
 5. The invention as defined in claim 2 characterized by said other end of said print hammer projecting beyOnd said pivot means, and further characterized by compression spring means engaging said projecting portion for biasing the print hammer to a rest position, said compression spring means being electrically connected to the operating coil for effecting selective energization thereof. 